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Override switch on cooling fan

Discuss your latest mods or ideas, and anything to do with the BMW X5 (E53).
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Rick G
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Override switch on cooling fan

Post by Rick G » Fri Jan 17, 2020 2:15 pm

I am looking at putting an override switch on the cooling fan of my E53 N62 4.4L. Some I have found put a resistor across the temp sensor and fool the DME that the engine is overheating then the fan cuts in but I found that on the K series bikes it also leans out the mixture and makes the ECU think there are problems and reacts by limp mode and other things like not starting if the engine is stopped and not let cool below the normal running temp.
Has anyone done this and if so how did you go about it.
I will be using the X5 to tow a big caravan in some fairly hot places so want to have a manual override to keep it cool and not cool it when it gets overheated.
This will be in the Aussie summers and 45°C days will be common.
Rick

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X5Sport
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Re: Override switch on cooling fan

Post by X5Sport » Fri Jan 17, 2020 5:55 pm

The auxiliary (a/c) electric fan uses PWM not a switched 12V supply to control the fan and it’s speed. Switching the supply won’t work. It could also cause the a/c to cut out.

I thought that the engine cooling fans were all viscous clutch coupled? Happy to be educated though.

Having just returned from Melbourne I thought the cars all had cooling only - not heating as well. :P

Having watched the fire situation with some horror and concern for those I met out there, keep safe.
:ant: Never anthropomorphise computers. They hate that.

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Rick G
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Re: Override switch on cooling fan

Post by Rick G » Sat Jan 18, 2020 12:12 am

It may be a hot climate only thing but from what I can see the E53 with the N62 (09/2003 to end of production) had just the electric fan behind the radiator and no engine driven fan.
Being PWM as I thought they might be is fairly easy to get around with the use of diodes to isolate the system from seeing the straight 12v, it's much like the later K series bikes which I am familiar with so I will give it a go.
Melbourne would have given you an eye opener to the bush fires here, I am about 800 miles north and we had a fire start about 2 miles away in September and have been very worried about any more until yesterday when we got almost 6 inches of rain so things are looking a bit better now except that the grass will go into overdrive and I will have to mow the yard for the first time in 12 months but I am happy to do that.
I have the heater going in winter here as -10°C is common overnight in the southern highlands of Queensland. The record temperature has been broken twice in the past 3 years here and is now 42.1°C and we are 1200meters above sea level.
I will post any results of my endeavours if and when I do something.

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Re: Override switch on cooling fan

Post by Themoog2 » Mon Jan 20, 2020 3:50 am

Doesn't the M62 have a big void in front of the rad unlike the N62 which has an electric fan there? If so then just install a second hand fan with a manual switch. I think..

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Re: Override switch on cooling fan

Post by Rick G » Mon Jan 20, 2020 5:20 am

The N62 doesn't have a fan in front of the radiator and that is where I have extra cooling for the engine oil and transmission oil so with 9" fans on each of those coolers there is no room there and towing a 24' van it needs all the cooling it can get. I like to have a manual override so that when I get to the bottom of a long up hill section I turn it on before the engine temp starts going up which gives it a head start.

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